Research And Design Of Multichannel Seismic Data Acquisition Nodes Based On FPGA

Petroleum resources are one of important energy sources for the development of national economy, and they are also vital strategic resources and impetus to the rapid development of economy. As the most effective method in the exploration of petroleum resource, seismic prospecting has been widely used in the exploration of complex mountains. The property of seismic data acquisition node poses a direct effect on the performance of seismic prospecting instrument as acquisition of seismic data is both an important indicator for the veracity and accuracy of seismic exploration and a vital element for data pick-up. Temporary storage technology of seismic data contributed a lot to the reliability and security of seismic data.Based on the demands of complicated mountainous seismic prospecting instrument towards acquisition nodes, this paper relies on the "the development of multi-wave and broadband seismic data acquisition system under complicated mountainous condition which belongs to important scientific instruments equipment developed special for NSFC. With FPGA as its dominant component and intelligent of seismic data acquisition as its design target by using Verilog HDL and top-down design method, presenting a scheme of multichannel seismic data acquisition node. By carrying out researches on parallel acquisition of multichannel seismic signals, temporary storage of large-capacity data combined with asynchronous FIFO and RS485 data transmission, some principal achievements are achieved in the paper, which goes as follows:(1) Research and design of acquisition node key circuit. FPGA, featured with high integration, timing accuracy and strong parallel processing ability, is selected as the core processor. ADS 1252, a 24-bits high resolution analog-digital converter is used to transfer analogue signals of seismic data into digital signals and related circuit is also designed. Asynchronous FIFO and large-capacity SDRAM temporary storage scheme is adopted to cache multichannel seismic data. Besides, SDRAM interface circuit and RS485 interface circuit are also designed in a detailed way.(2) Research and design of ADC controller. With FPGA as the main controller, it achieves logic control towards ADC and gets sampling data characterized with high precision and wide dynamic range. Finite-state machine is used to control parallel sampling operation of multichannel ADC, which enables the system with advantages of strong real-time performance, high resolution and low interference noise etc. Through simulation and online testing towards ADC sampling and analysis and comparison to matlab simulation, stability and reliability of the multichannel seismic data acquisition node has been verified.(3) Research and design of asynchronous FIFO memory. With FPGA as the main controller, detailed analysis towards asynchronous FIFO storage structure was presented and discussion about all modules was also taken to explore key problems in the design. The application of synchronizer greatly reduced the probability of metastable condition and application of Gray code conversion technology guaranteed the reliable transmission of data, improving the design efficiency. Practicability and high efficiency of asynchronous FIFO have also been verified by read/write simulation and contrast tests towards it.(4) Research and design of SDRAM controller. With FPGA as the main controller, FSM has been used to describe SDRAM core control logic, improving the design efficiency and simplifying the control logic. The combined application of high-capacity SDRAM and high-speed processing FPGA improves speed of the system and saves system resources. Online test and analysis towards SDRAM memory fully proved the accuracy and pracability of the SDRAM read/write operation.(5) Research and design of RS485 controller. With FPGA as the main controller, in order to guarantee the effectivity and availability of this system, this paper did much work in the logic design of receiving and sending module.In conclusion, multichannel seismic data acquisition node illustrated in the article can be applied in seismic exploration equipment effectively. Its advantageous performance and flexibility verified by practices proved its practicability and value for popularization.